Do big numbers mean big cash? Shooting super-telephoto images

Today, I thought I would turn away from macro and taking photos from really close-up, to taking photos of things from really far away…

Like macro, taking shots with “super-telephoto” lenses can very easily be written off as a rich man’s game – and there are definitely plenty of rich boys’ toys out there if you have bottomless pockets. For example, a story recently surfaced of a £99,000 telephoto lens going on sale!

If you’re anything like me, though, you’re probably looking for a solution for under £100. Okay, so that’s hardly free, but this is a specialist area.

But what are your choices? Well, actually – there are quite a few.

In the case of the (slightly daft) £99,000 lens, the focal length on offer was an enormous 1,200mm – and the lens (as a result) was totally impractical for most purposes. However, there are times when you’re shooting wildlife, sporting events or some specific scenery when you may want something which is pretty far reaching. In these cases, it’s actually quite handy being on a budget as most cheaper cameras have smaller sensors which effectively increase the effective focal length of a lens, relative to a 35mm SLR or full frame DSLR. This basically means that you get more magnification in your final shot from the same lens. In the case of most Canon EOS cameras, you get a magnification (known as a “crop factor”) of 1.6X. For a Nikon you get 1.5X. For some bridge cameras, the crop factor may be as high as 5X to 6X!!

“it’s actually quite handy being on a budget as most cheaper cameras have smaller sensors which effectively increase the effective focal length of a lens…”

But what does it really mean? Well – I’m going to look at focal lengths of between 500 and 800mm (equivalent for a 35mm camera). This is because there are lots of ways of getting lenses of around 500mm of an APS-C DSLR which, because of the crop factor, will give the same level of overall magnification in your final shot as an 800mm lens on an old film SLR.

I’ll mention five options, and test four:

Supplementary telephoto lenses

Teleconverters

Manual focus mirror lenses (often t-mount)

Manual focus multi-element telephoto lenses (often M42 mount)

Superzoom bridge cameras

1. Supplementary telephoto lenses – from as little as £10 on ebay

I said I’d mention but not test one option – and this is it. Supplementary telephoto lenses screw in front of the lens of your camera (like the diopters I tested for macro), or many wide angle or fisheye adapters. I have already tested diopters on this website, and I will return to supplementary fisheyes in the future – but I’m not going to test the telephoto version because they are simply too rubbish. My three pieces of advice would be avoid, avoid, avoid. The real issue is that, unless you have a tiny aperture (and therefore have to push up the ISO and exposure time up beyond a practical level), you get terrible focus problems anywhere outside dead-centre of the frame. If you would like to see some tests demonstrating this – I would point you to Keith Cooper’s article here. (Seriously, though, even for £10, don’t bother.)

2. Teleconverters – Prices vary a lot, though if you shop around you can start from around £25 second hand.

In terms of intended outcome, teleconverters do the same thing as supplementary lenses – in so far as they work with an existing lens and increase its effective focal length. The mechanism by which they do this is far more effective, though. Rather than acting as a “magnifying glass” at the front of the lens, they work as an additional lens element stage between the sensor and the lens. While it is obviously not as good as an expensive, dedicated telephoto lens, it is still pretty effective and a lot cheaper!

Now – one clear challenge here, is that in order to use a teleconverter to reach super-telephoto length, you will already need to have a telephoto lens with a focal length of around 250mm to start with. These can also be expensive, but there are some cheap second hand options out there. A few examples are:

In my test case, I have coupled a second hand Jessops (Kenko) teleconverter (bought for £25) with a Canon EF 75-300mm lens, bought second hand for £50, so £75 in total. I also have the Tamron lens, which works equally well (perhaps a little better). The photos used in this test aren’t terribly exciting, but they were all taken at the same time, in the same light so give a fair representation of capabilities:

Test – 2x Teleconverter with 75-300mm Canon telezoom.Shot at around 500mm on an APS-C camera (800mm equivalent on a full frame camera). At this focal length the auto-focus stops working.

The focus achieved, given the long focal length is acceptably sharp, and chromatic aberration is not too noticeable (though from experience, this gets a log worse as contrast in your image increases).

Pros:

Pairing a tele-converter with a zoom means you can have an enormous range of zoom available to you by simply adding / removing the converter. In this case, all the way from 75mm – 600mm.

Very space efficient, and can be paired with several different lenses. It can simply be kept in your kit bag alongside your main lenses.

Reasonable quality results, retaining aperture control for depth of field control.

Cons:

While auto-focus works at shorter focal length, once you have gone up to super-telephoto lengths it gives up, so manual focus only. Focus confirm should still work, though.

Adding a teleconverter reduces the light which reaches the sensor, so you will need to up the ISO, or lengthen exposure time unless it’s very bright. At long focal lengths, this can be tricky. You will probably want a tripod! (Though I would recommend it for all of these solutions really…)

Until recently, I had never tried a mirror lens, and I had always been fascinated by the idea of them. If you look at a mirror lens from the “front” they really mess with your mind. How can you get a full image from a lens which looks like it still has a small lens cap stuck in the middle of it? (I’ll let you ponder that on your own).

Mirror lenses used to be very popular as a cheap way of getting up to super-telephoto focal lengths, without enormous costs. Their relatively simple construction, basically consisting of two carefully aligned mirrors, means that there is far less complicated and heavy glasswork to create the image. The lenses are also much, much shorter than multi-element telephoto zooms. High grade mirror lenses remain very popular with astro-photographers, because they are virtually free from chromatic aberration and some of their weirder properties (donut shaped bokeh and “double vision” either side of the optimum depth of field) disappear at infinity focus.

But can they be used for day-to-day use? – On this occasion, I can’t exactly say that I’m convinced. I should say that I have only ever used one (so not a statistically brilliant sample), but it is a very common one – the Opteka 500m f/8, t-mount (don’t forget to buy the right adapter!) I bought mine new and I believe it to be in “perfect” working order – but there are some serious limitations to optics of this type.

The major problem is low contrast (caused by the shadow of the front mirror), but this in turn makes it very difficult to find focus and, to be honest, I am not convinced that the sharpness of this sort of lens is ever really up-to-scratch. That said, I have managed to get a few nice shots, and the low contrast can be corrected in post-processing. For a fair comparison, below is an unprocessed shot, straight from the camera:

Opteka 500mm f/8 mirror lens. The shot shows the low contrast caused by the mirror’s shadow, which can be corrected in post-processing, and the “double vision” background, which cannot.

Pros:

Virtually no chromatic aberration (so good for astro-photography).

Very small for a dedicated super-telephoto lens.

Cheaper than buying a standard tele-photo lens plus a converter

Cons:

Donut bokeh and double-vision backdrops

Low contrast and can be hard to focus

Can seem a bit soft generally (though that could just be me!)

Normally fixed f/8 aperture, so no control over depth of field.

Before moving on, though, it would be wrong of me not to show an image of something I believe that they are good at!

Opteka 500mm f/8 mirror, in this case paired with a 2x teleconverter giving a whopping 1,000mm focal length (1,600mm equivalent on full frame). The image is virtually free from Chromatic aberration, which would be a major problem with a multi-element optic.

I should start this section by saying I think I got an absolute bargain, having picked up an Optomax Telephoto 500mm f/8-f/32 lens for just £25. In my case the rear element (closest to the camera) has gone a little bit milky, but even with this problem it seems optically very good (so I would love to try a mint one!) Keep your eyes peeled for a second-hand bargain.

The costs of this sort of lens (often M42 to t-mount, so again, don’t forget the right adapter) vary quite a lot – but these generic lenses are much, much cheaper than branded auto-focus lenses. Rokinon are the modern makers of a basically identical lens, and you can buy them new from around £80 if you shop around. They are manual focus, and have manual aperture control (but this is important, as they aren’t fixed at f/8). They also make a super-tele zoom (Rokinon 650-1300mm, normally sold with a 2x tele-converter), which you can pick up from around £150 new. You will need to shop around for this.

The construction is pretty simple, and they can be taken apart almost completely, simply by twisting and unscrewing (which can be handy if you want to pack them away somewhere not at full length). They are pretty long and unwieldy and normally come with their own tripod mount.

The image quality from these is pretty good if you are patient enough and good at manual focus. Shooting handheld can be very tough though because of their length – so if you are trying to catch fast-flying birds, it may be a bit difficult.

All of the other options I have looked at today assume that you already have a camera to attach a lens to. This is a one-stop-shop solution and is therefore very convenient for travelling light. I am a big fan of bridge cameras as “good all rounders” and the modern superzooms are truly impressive in their equivalent focal-length range.

You will see in the photo below, that the equivalent focal length is not quite as large as I was able to achieve in the tests above, but I was using my old fuji Bridge camera (with an 18x optical zoom) and some newer bridge cameras can come with up to 50X optical zoom. In this case, my Fuji S8000fd has a focal length of 4.7 – 84.2mm which doesn’t sound much, but with a 5.6X crop factor, it gives a 35mm equivalent focal length of 24-486mm, which is pretty impressive. You can buy newer version for under £100 with 30X zooms which is equivalent to 24-720mm so the numbers are getting pretty big!

Of course, the downside is that the sensor is small and therefore the ultimate clarity and light sensitivity of the camera will suffer, and if autofocus doesn’t lock on, manual focus can be a dead-loss, but in good conditions, things are pretty good.

Fuji FinePix S8000fd at full zoom (84.2mm, equivalent to 486mm full frame). Newer bridge cameras can zoom in even closer.

Recommendation?

As ever, your final choice is up to you – there are advantages and disadvantages to each solution. Here are my thoughts in summary though:

Never buy a supplementary lens for your filter ring. You may as well burn a £10 note.

Personally, I would never build a DSLR camera bag and not include a 2x teleconverter. Sure, they may not be as good as a massive, expensive lens, but they’re cheap and portable, so you can take them with you everywhere.

If you don’t mind the length, the fixed focal length M42 mount lenses from Rokinon and Optomax etc. are really good for the price.

Bridge cameras remain great all-rounders provided you aren’t too fussed about retaining total control (or taking portraits with lovely narrow depth of field at shorter focal lengths). Plus, the lens and the camera come together, so if you don’t mind an old 8 megapixel one they’re an absolute bargain.

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